leonard



L'. V. LEONARD.

ELECTRIC HEATER UNIT.

APPLICAUON FILED JULY a, 1919.

1,373,895. Patented Apr. 5, 1921.

2 SHEETS+SHEET 2.

UNITED STATES PATENT OFFICE.

ELECTRIC-HEATER UNIT.

Specification of Letters Patent.

Application led July 1, 1919. Serial No. 308,043.

To all 'whom it may concern.'

Be it known that I, LESLIE VICTOR LEON- ARD, a subject of the King of Great Britain, residing at Richmond, Victoria, Australia, have invented certain new and useful Improvements in Electric-Heater Units, of which the following is a specification.

This invention relates to electric heater units adapted for use as radiators, heating and cooking stoves, toasters and the like, and is more particularly applicable to heaters of the type in which resistance wires are carried by refractory supports so arranged that the radiant and reflected as well as the convective heat, is concentrated and given off in the direction required.

The chief objects of my invention are to increase the amount of radiant heat available in units of this type in proportion to the length of the resistance wire employed, thereby making it possible to produce a very high temiperature in the immediate neighborhood of the heater; to provide means for cooling the terminals of suoli heaters and protect them from the eXtreme heat generated; to construct heating elements which are more compact, lighter and cheaper than existing structures of the same type; to arrange the elements in such a manner that substantially all the primary or directly radiated heat is emitted in one direction and may be applied, without appreciable loss, to the bottom of a kettle or other container placed on the heater; and, in brief, to provide an electric heater embodying such features as are desirable iii portable stoves, cooking utensils, toasters, and other appliances which are required to be easy to handle, and to produce a uniform and very intense heat in the immediate vicinity of the apparatus.

With these objects in view, I arrange one or more insulating refractory bodies or members on a refractory base in such a manner that air may circulate between the base and said member or members, and I wind a resistance wire on the exposed side of each of said members, looping the wire around suitable projections on the edges of the supporting member and stretching it back and forth from one edge to the other.

In carrying out my invention, I use wire supporting members consisting of flat or n curved plates, preferably in the form of longitudina'lly divided tube sections, having substantially parallel longitudinal edges lili'dbadapted) Eo orliln, in conjunction with e ase, su s an ia tubular assa the air to be heated. y p ges fol n .In the preferred structure the base coinprises a shallow dish-shaped block of porcelain or like refractory material, having a smoothor grooved concave surface adapted to receive the edges of a series of wire supporting members arranged thereon in radial relationship, the wires then being connected to a series of terminals symmetrically disposed around the center of the unit in a wellvknown manner.

The'air to be heated in the tubular passages is preferably admitted through suitable perforations in the base arranged in proximity to the terminals, which are thus cooled by a continuous circulation of fresh air. a Referring to the accompanying drawings in which I have illustrated, bv way of eX- ample, an embodiment of my invention:

Figure 1 is a partial plan view of a heating unit according to my invention; y

Fig. 2 is a sectional elevation on line 2-2 of Fig. 1;

Fig. 3 shows one yof the wire supporting members in elevation, on an enlarged scale; Figs. 4 and 5 are sectional views of the supporting member shown in Fig. 3, Fig. f1 being a longitudinal section, and Fig. 5 a cross-section on line 5 5 of Fig. 3; and Figz is a fragmentary perspective view of a slightly modified structure.

' The heater unit illustrated in Figs. l to 5 comprises a base 10, of porcelain or other suitable heat resisting insulating material, having a concave upper surface Yl1 adapted to receive a number of wire supporting members 12 of like material, six such members Patented Apr. 5, 1921. i

being placed in radial relationship in the Y example shown. The concave surface 1l has substantially the shape of an inverted truncated cone which, in the preferred contions 12 are suitably curved to fit the curvature of the surface 11, so thatwhen said sections rest with their edges on the concave surface of the base thej.7 form in conjunction therewith a series of air passages radiating from the center of the unit. At their outer ends 14 the tube sections 12 are splayed so that the outer openings of the air passages are approximately perpendicular to the axial line 9-9 of the unit (Fig. 2).

A resistance wire 15 is wound on each member 12 in such a manner that the whole length of the wire faces the side of the heater on which the heat is to be utilized. To this end the members 12 are provided externally with a. series of parallel grooves 1G and their edges are formed with a row of small teeth 17 separated by notches which coincide with the ends of said grooves. As shown in Figs. 8 and 4, the wire 15 is seated in the grooves 16 and looped back and forth around the teeth 17. The outer end of the wire extends through a hole 18 in the mem ber 12 and is led back toward the center of the unit along the inner surface of the member 12.

Inside each member 12, at the inner end thereof, is fitted a refractory insulating block 19 which is fastened thereto by suitable means, such as a screw 20. To this block are secured by screws 21 and nuts 22 a pair of contact limbs 23, 24 provided each with a screw 88 adapted to engage'one end of the wire 15. Each supporting member 12, with its resistance wire 15 and contact limbs 28, 24, constitutes an interchangeable element adapted to be electrically connected to and held in position by engagement with suitable terminal pieces in the base 10.

To this end the contact limbs 23, 24 are each provided with a boss 25 and eye 26 adapted to engage one of a pair of pin terminals 27, 28 mounted in the insulating base 10. r1`he terminals 27, 28 are arranged in a circular row, as shown in Fig. 1, adjacent pairs being connected by contact plates 29. Two diametrically opposed pin 'terminals extend through the base 10 and terminate in plugs 80, 31 adapted to bey connected to a supply of current. With this arrangement of the terminal connections, which is described by way of example only and does not form part of the present invention, the'radial elements form two sets of three in number, each set being wired in series with the source of supply.

To protect the terminals, I use a cover 32, of porcelain or like insulating material, adapted to be fitted on a stud 38 secured in the base 10 centrally thereof and having a threaded upper end to receive a knurled nut 34 for securing the cover in position. On account of the comparatively small vertical dimension of the wire supporting members according to this invention, I am enabled to arrange the cover 32 so that it will bear on the bosses 25 on the contact limbs 23, 24, instead -of resting on the wire supporting members, as was the case in prior structures. In this manner the members or sections 12 are relieved from external strain and the pressure exerted by the cover insures a more efficient engagement between the Contact limbs and the plates 29. Suitable rounded notches 39 are provided in the periphery of the cover 32 to accommodate the tube sections 12.

The air to be heated in the passages between the tube sections and the base is preferably admittedthrough a series of holes 35 in the base 10 arranged in proximity to the terminal connections for the resistance elements. These connections, thus, are cooled by the incoming air and effectively protected from the action of the extreme heat generated in the unit.

The base 10 may be surromided with a easing of sheet metal 36 supported by suitable legs 37.

The members or sections 12 may be substantially hemi-cylindrical, as stated above, or they may be in the shape of a more or less'flattened segment, or of a plate. Fig. 6 illustrates a modification of the invention in which the wire 15 is wound back and forth on the exposed sideof a rectangular supporting plate 42 and looped around proj ections or teeth 43 on opposite edges thereof. In order to provide suitable passages for the air to be heated, grooves or channels 44 radiating from the center of the unit are formed in the base 40, and a plate 42 is fitted over each of such channels in the manner illustrated. The plates 42 carry insulating blocks 49 similar to the blocks 19 and adapted to receive contact limbs such as those described above. As will be understood,the general arrangement of the unit and its terminal connections may be the same vas in the embodiment illustrated in Figs. 1 to 5, and need not be further described.

When the appliance is in use, a body placed thereon or held above the same is exposed to the direct radiation from all the wired surfaces. In addition thereto any heat radiated into the air passages is refected outwardly by the base,kand a circulation of air is set up through the holes 35 and air passages, the heated air issuing therefrom surrounding and tending to oppose any diffusion from the Zone of intense heat facing the wires 15. IVith a cooker of ordinary size consuming, say, 66() .vatts.v thetemperature in said Zone is sufficient to igniteV a piece of paper held over the apparatus.

On account of its shallowk and compact structure and the high temperatures obtainable, the heater described is of particular advantage for boiling, toasting and cooking purposes, but it will be understood that it 'may be used equally well for other purposes, and that various changes may be made therein withoutdeparting from the scope yof the invention asset forth in the appended claims.

I claim: f i

l. In an electric heater, a refractory base, an insulatingrefractory support arranged on said base so as to permit of air circulating therebetween and from the under to 3. In an electric heater, a refractory base,

an insulating refractory support having substantially parallel edges resting on said base and forming a passage through which air may pass from the lower to the upper side of the base, and a resistance wire wound n wholly on the side of said support remote from said base.

4t. In an electric heater, a refractory base, a curved plate of linsulating refractory material on said base, the concave s'ide of said plate facing said base so as to form a passage through whichair may pass from the` lower to the upper side ofthe base, and a resistance wire woundy wholly on the convex side Of said plate.

5. In an electric heater, a refractorybase, a series of insulating refractory members radially arranged on said base and forming therewithy substantially tubular air passages through which air may pass longitudinally from the lower to the upper side of the base, and a resistance wire wound wholly on the exposed side of each of saidmembers. v 6. In an electric heater, a shallow dishshaped base of insulating refractory material, a plurality of longitudinal tube sections of like material resting with their lonlgitudinal edges on said base so as to form` passages through which air may pass from `the lower to the upper side of the base, and resistance wires wound wholly on the outer sides of said sections.

"7. In an electric heater, a refractory base having a concave face shaped as an inverted truncated cone merging into a curve near its periphery, a plurality of insulating wire ueupporting members radially arranged on said base, shallow air passages between said base andsaid members and leading from the under tothe upper side ofthe base, and resistance wires wound wholly onthe sides yof said members facing away from said base.

insulating refractory members'arranged on said base so aste form therewith a seriesl of tubular air passages, resistance wires on 'the exposed sides of said members, terminals carriedxby said base, and connections between said wires and terminals, air ,holes being .provided in the base` adjacent said terminals. n i

9. In an electric heater, an insulating refractory base, insulating refractory members radially arranged on said base and forming therewith a series of tubular air passages through which air may pass from the under to the upper side of the base, resistance wires on the exposed sides of said members, terminals lcarried by said base, contact limbs between said wires and terminals, and a cover adapted to bear on said contact limbs.

l0. In an electric heater, a refractory base, a plurality of longitudinally divided tube sections having toothed longitudinal edges resting on saidV base, and resistance wires looped around the teeth on said edges and wound wholly on the exposed sides of said tube sections.y

ll. In an electric heater, a dish-shaped base of insulating refractory material, a plurality of longitudinal tube sections of like material radially arranged onsaid base and having `their longitudinal edges in engagement therewith, resistance wires wound on the outer sides of said tube sections, terminals carried by said base, contact limbs between said wires and terminals, a refractory cover extending over said terminals andk adapted to bear on said contact limbs, said cover having roundednotches in its periphery for accommodating said tube sections.

l2. In an electric heater, an interchangeable element comprising a longitudinally divided tube section of insulating refractory y i material having toothed longitudinal edges, a block of like material fitted in and secured to said tube section at one end thereof, a pair of contact limbs carried bysaid bloclgand a resistance wire connected to said contact limbs and wound wholly on the outer side of said tube section.

A13. In an electric heater, an interchangeable element comprising a support of insulating refractory material having substantially parallel longitudinal edges, a resistance wire wound wholly on one side of said support, the outer endof said wire being led said air holes toward the periphery -of Said ractory Cover adaptedto bear on saideonf hase, and resistance Wires arranged over said tact limbs, air passages extending from under .10 J

passages, all said wires facing upwardly. said cover toward the periphery of said base, l5. In an electric heater, an insulating re- ,resistance Wires Connected to said Contact fractory hase, terminals on Said base, Contact limbs and arranged over said passages, and plates connecting adjacent pairs of' termimeans for cooling said terminals.V nals, Contact limbs engaging each terminal y f In testimony whereof I afix my signature. 15 and bearing on said plates, an insulating re- LESLIE VICTOR LEOIIARD. 

